This proposal is designed to study the role of non-neoplastic suppressor cells in the secondary immunodeficiency associated with cancer and other human diseases. An emphasis will be placed on the role of soluble suppressive factors such as prostaglandins and the mechanisms of interaction between tumor cells, lymphocytes, non-lymphoid cells, and agents such as viruses and interferon on the modulation of suppressor cells. Specifically, we plan to investigate the induction of prostaglandins in non-lymphoid cells by measles virus infection and the interaction of such cells with lymphocytes. In addition, family members of cancer patients will be studied for abnormalities of prostaglandin-producing suppressor cells or natural cytotoxicity. Cancer patients with abnormalities of suppressor cells will be serially studied to determine the effect of therapy on these in vitro assays. Finally we will investigate how natural cytotoxicity can be modulated by prostaglandins and other agents.